Americans have been stepping up efforts to keep their data private since the revelations about vast US government surveillance programs, a survey showed Monday.

The Pew Research Center survey showed 30 percent of US adults had taken steps to shield their information from unwanted attention.

And 22 percent said that they have changed how they use technology or social media since the leaks by former National Security Agency contractor Edward Snowden in June 2013.

Lee Rainie, who heads Internet studies at Pew, said the survey showed Americans are "adjusting some activity at least in some simple ways like changing their privacy settings and being a bit more discreet in the things they say and search for."

About one in six said they had changed how they use email, search engines or social media, Pew found. Others said they had made changes in their use of cell phones, mobile apps, texting or landline telephone use.

The changes included modifying privacy settings on social media or using social media less often. But 15 percent said they had have avoided certain apps and 13 percent have uninstalled apps due to privacy concerns.

And one out of seven surveyed indicated they speak more in person instead of online or on the phone or avoid using certain terms in online communications.

- More complex passwords -

"A notable share of Americans have taken specific technical steps to assert some control over their privacy and security, though most of them have done just simple things," the survey authors wrote.

"For instance, 25 percent of those who are aware of the surveillance programs are using more complex passwords."

But Pew researchers found a majority of Americans did not take advantage of more powerful privacy tools such as encrypted email, proxy servers or anonymous search engines. In most cases, the respondents were unaware or these tools or felt they were too complicated to use.

For example, just two percent said they had used anonymity software such as Tor, with the vast majority either not considering its use or unaware of the tool.

- Split on surveillance -

The survey showed mixed views about the merits of government surveillance.

Nearly nine of out 10 surveyed said they had heard about the government monitoring and 52 percent said they were "very concerned" or "somewhat concerned" about the programs.

But 46 percent said they were "not very concerned" or "not at all concerned."

Asked whether it was acceptable to monitor the communications of Americans, 57 percent said it was not, while 40 percent said it was OK.

But 54 percent said it was acceptable to monitor citizens of other countries, and 60 percent said they saw no objection to surveillance of American or foreign leaders. Eighty-two percent said surveillance of terrorism suspects was acceptable.

Some 475 US adults were surveyed between December 2014 and January 2015, Pew said, with a margin of error estimated at 5.6 percentage points.